03 软件10-1班 201003031006 李冉 外文翻译

1、齐 鲁 工 业 大 学外文资料及中文译文院系名称 信息学院 学生姓名 李冉 学生学号 201003031006 专业班级 计科（软件）10-1 指导教师 刘嵩 二一四 年 四 月 六 日外文资料A survey on web services composition_Dustdar_Schreiner_inPressAn orchestration model defines abstractions and languages to define the order in which and the conditions under which web services are invoke

2、d. Orchestration models use process-modelling languages, such as UML activity diagrams, Petri-nets, state-charts, 4 S. Dustdar and W.Schreiner rule-based orchestration, activity hierarchies, and -calculus. Data and data access models define how data is specified and exchanged between components. The

3、 service selection model deals with static and dynamic binding that is how a web service is selected as a component, statically at design-time or dynamically during run-time. Transactions define which transactional semantics can be associated to the composition and how this is done. Finally, we must

4、 also consider a model for exception handling to handle exceptional states during the execution of the composite service without the service being aborted.The Business Process Execution Language for Web Services (BPEL4WS) standard proposed by IBM (Virdell, 2003), Microsoft and BEA (Andrews et al., 2

5、003) is in many cases related to former standards, such as WSFL or XLANG. BPEL descriptions are XML documents, which describe the roles involved in the message exchange, supported port types and orchestration, and correlation information as aspects of a process. BPEL4WS is a service composition mode

6、l (Wohed et al., 2003), which supports both, composition and coordination protocols. It also consists of an activity-based component model, an orchestration model that allows the definition of structured activities, XML schema data types, a service selection model and a mechanism for exception, even

7、t and compensation handling.3 Managing a film crew: a case studyAccording to Dustdar and Treiber (2004) the case study of managing a film crew has been selected, in order to explain the different concepts and frameworks introduced in various papers, with a consistent reference scenario that runs thr

8、ough the whole paper.Basically, a film crew consists of one or more film directors, external experts and crew-members. Each of these teams provides particular services and work together in a loosely coupled way, providing their expertise on demand, while they depend on the services provided by other

9、 film teams.A film director must coordinate the film teams, is responsible for the budget, and must enable communication among different teams. Since different phases in the film production place different requirements on the arrangement of the teams, each phase requires flexible composition and con

10、figuration of the film teams. Directors hire film crews and external experts who provide own services and capabilities necessary for shooting a film. External experts offer their expertise on several topics, such as physics, health, or law to make the film and special effects more realistic. Crew-me

11、mbers may act as stuntmen for example.4 Composition issuesWeb service composition (Benatallah et al., 2001, 2002) is a very complex and challenging task, as will be seen when discussing different composition approaches in greater detail. Before performing web service composition, some basics to enab

12、le service composition have to be performed. Six different issues that have a large impact on service composition have been identified. The following sub-sections do not claim completeness of composition issues. The most important issues may be explained in a few words. The concepts, some standardis

13、ation efforts and related research work as well have been introduced. Sun Microsystems, for example, has proposed standards for coordination (Terai et al., 2003), transaction, and context and has put them together to one comprising standard called WS-CAF (Web Services Composite Application Framework

14、) (Bunting et al, 2003b).Coordination, transaction, context and conversation modelling is discussed. When composing services composite service execution must be considered. Centralised and distributed service execution has been differentiated, and frameworks that fall into these categories have also

15、 been discussed. In addition to the traditional SOA (Service Oriented Architecture) mentioned in the introduction-based infrastructure, there are also alternatives to that. Here, peer-to-peer infrastructure is dealt with and a P2P based framework called Peer-Serv is described, and suggestions to ext

16、end the classical web service model in order to precisely describe web services and facilitate quality driven service discovery (Benatallah et al., 2004a) are presented4.1 CoordinationThe basic web service infrastructure presented in Section 1 satisfies simple interactions and method invocations amo

17、ng interacting entities. When it comes to composing web services and building complex software systems, it is likely that interaction requires coordination of sequences of operations, to ensure correctness and consistency. New protocols and abstractions are needed and this is exactly the case of coo

18、rdination. In order to provide modelling abstractions and simplify web service development, different standardisation efforts, such as WS-Coordination (Cabrera et al., 2002) by IBM or WS-CF by Sun (Bunting et al, 2003a) have been taken.4.2 TransactionTo add guarantee to the interactions, it is of co

19、nsiderable importance to add a transaction (Papazoglou, 2003) protocol to the coordination framework in order to provide short-duration transactions, called atomic transactions, and long running business activities as well. In case of long running activities, it is not always possible to ensureACID

20、(atomicity, consistency, integrity, and durability) properties of web service transactions. Very important to name are the WS-Transaction (Cabrera et al., 2001; Freund and Storey, 2002a, 2002b) standard, proposed by IBM and WS-TXM (Bunting et al, 2003c) suggested by Sun. WS-Transaction builds upon t

21、he WS-Coordination framework mentioned above, since it defines protocols for centralized and peer-to-peer transactions, both of which require the existence of coordination.4.3 ContextThe term context is a very vague one, since many different definitions can be found in literature. In terms of web se

22、rvices, context maybe inferred as information utilised by the web service to adjust execution and output to provide the client with a customised and personalised behaviour (Keidl and Kemper, 2004a; Álvarez et al., 2003). Context is extensible with new types of information at any time, without a

23、ny changes to the underlying infrastructure. Context may contain information such as a consumers name, address, and current location, the type of client device, including hard- and software that the consumer is using, or all kinds of preferences regarding the communication.The WS-Context (Bunting et

24、 al., 2003d) standard, which is part of the WS-CAF standard proposed by Sun, specifies context, context sharing, and context management.中文译文业务流程模型通过定义抽象和语言来定义命令，以及web服务被调用的条件。业务流程模型使用流程建模语言，如UML活动图， Petri网，状态图，以4 S. Dustdar 和W. Schreiner规则为基础的业务流程，活动层次结构和演算。数据和数据访问模型定义数据是如何规定的和组件之间的转换。服务选择模型处理静态和动态绑

25、定Web服务器如何被选择为一个组成部分，在设计阶段是静态的，在运行阶段是动态的。事务定义了事务语义可以关联到的组成以及如何做到这一点。最后，我们还必须考虑一个用于异常处理的模型在组合服务的执行不被中止服务情况下处理异常状态。业务流程执行语言是针对Web服务（BPEL4WS）标准，由IBM（Virdell，2003），微软和BEA（Andrews等，2003）提出的，许多内容是与之前标准相关的，如WSFL和XLANG。业务流程执行语言描述的是XML文档，它描述了消息交换，支持的端口类型和业务流程，以及相关的信息作为各个方面的一个过程中被调用的规则。BPEL4WS是一种服务组合模型（Wohed等，

26、2003），同时支持， 组成和协调协议。它还包括一个基于活动的组成部分 模型，业务流程模型，它允许结构化活动的定义，XML 架构数据类型，服务选择模型和机制的异常，事件和 赔偿处理。BPEL4WS是一种服务组合模型（Wohed等，2003），它同时支持组成和协调协议。它还包括一个基于活动的组成部分的模型，一个允许结构化活动的定义的业务流程模型，XML架构数据类型，一个服务选择模型和异常处理，事件和 赔偿处理机制。3管理摄制组：案例研究根据Dustdar和Treiber（ 2004）管理一个电影摄制组的案例研究被选中，目的是为了解释不同的概念和框架结构被引进到各种论文，一致的参考情节贯穿于整个论

27、文。基本上，一个电影摄制组由一个或多个导演，外部专家和组员组成。每个小组提供特定服务并以紧密的方式协同工作，提供他们被需求的专业知识，而他们依赖于其他电影团队所提供的服务。电影导演必须协调电影队，负责预算，并且必须使不同的团队之间的沟通。在电影制作的不同过程中，导演会给各个小组分配不同的任务，每个阶段都需要电影团队灵活的分工和配合。导演聘请摄制队和外部专家为拍摄场景提供必要的服务和功能。外部专家为一些主题提供他们的专业知识，如物理，健康或法律使电影和特效更加逼真。剧组成员可作为特技演员的例子。4组成问题Web服务组件（ Benatallah等人， 2001 ，2002）是一个非常复杂和挑战性的

28、任务，如讨论更加详细的处理不同的组件的时候可以被看到。在执行web服务组件之前，一些能够使服务组件可用的基础必须被执行。六个对服务组件有很大的影响的不同的问题已得到确认。下面的小节并不主张组件问题的完整性。最重要的问题可以用几句话来解释，一些标准化工作及相关研究工作也被引入到概念里。例如Sun Microsystems，提出了协调标准（Terai等， 2003年） ，将事务和内容放在一起构成的标准称为WS -CAF（Web服务复合应用框架） （Bunting等人， 2003年） 。协调，事务，内容和会话模型被讨论。当组件服务组合服务的执行必须加以考虑。集中式和分布式服务执行已经被分化，属于这些类别的框架也已经进行了探讨。除了在引入的下层构造中提到的“传统”的SOA （面向服务的体系结构） ，对此也是可供选择的。在